This invention in general relates to metallic substrates and metallic housings and, more particularly, to a method and apparatus for securing a metallic substrate to a metallic housing to provide a hermetic seal.
Engine mounted electronic control modules for vehicular engines are subject to a high level of heat and vibration. In these applications, electronic components and circuits are formed on a metallic substrate that typically needs to be enclosed within a hermetically sealed metallic housing. In the past, it has been costly to provide a hermetic seal at the joints of the electronic control module.
Aluminum is a preferred material used for metallic substrates and metallic housings for electronic control modules. Aluminum is cheaper than other metals and has a high thermal conductivity needed in automobile environments.
In assembling the metallic substrate and metallic housing, it has been known to use mechanical fasteners such as screws. However, this does not provide a hermetic seal.
Prior attempts at creating a hermetic seal have included plating, brazing or welding the aluminum surface with a metal layer such as zinc, copper or nickel. The cost for plating and welding, however, is expensive because it requires the use of plating and welding equipment. Additionally, the plating quality is very sensitive to the surface condition of the aluminum. The quality of welding is very sensitive to the gap distance at the joint or seam line between the pieces. Further, aluminum-brazing methods typically require inert atmosphere to operate.
It is also known to use special soldering processes suitable for aluminum, including high temperature solder and special fluxes. The cost involved in these applications, however, are also high because of the need for high soldering temperatures and special fluxes.
It is further known to use organic materials such as adhesives. The use of organic materials, however, may create weaker joints than a soldering connection. Additionally, known uses of organic materials is limited because they do not provide a hermetic seal. Further, the dispensing and curing of the organic materials complicates the production flow and adds more cost.
In sum, current devices and methods to join aluminum pieces are costly. Accordingly, there is a need for improved ways to provide an approach that reduces the complexity of the manufacturing process and reduces costs. This is especially important in high volume applications such as electronic control modules for vehicles. It is, therefore, desirable to provide an improved device and method of securing a metallic substrate to a metallic housing to overcome most, if not all, of the preceding problems.